0. Population Ecology Review:
Objective: 12D Recognize that long-term survival of species is dependent on changing resource bases that are limited
Review:
Population - a group of organisms, all of the same species living in a specific area.
Density - # of organisms
3 important characteristics of a population are:
distribution
density
growth rate

1. the number of individuals per unit area 1
Population density –
the number of individuals
per unit area
3 factors that can affect population:
- number of births
- number of deaths
- number of individuals that enter or
leave the population
Immigration – movement of individuals into an area
Emigration – movement of individuals out of an area

2. Population Growth of Houseflies
1 million
500,000
100
One year
Population size 2
J-shaped growth curve
— illustrates exponential population growth
Exponential growth – occurs when the individuals in a population reproduce at a constant rate
(as a population gets larger, it also grows at a faster rate)
No limits on growth
Under ideal conditions with unlimited resources
Could not occur forever in nature

3. Logistic growth – occurs when a population’s growth slows or stops 3
Logistic growth – occurs when a population’s growth slows or stops
- as resources become less available, following a period of exponential growth
Exponential
Limits on growth
A S-shaped curve illustrates logistic growth

4. Carrying capacity 4
Carrying capacity – largest number of individuals of a population that a given environment can support

5. Limiting factor – a factor that causes population growth to decrease5
Limiting factor – a factor that causes population growth to decrease
Any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms
Examples
Lack of food (energy)
Overcrowding
Competition for resources
(space, water, oxygen, etc.)

6. 2 kinds of limiting factors:6
2 kinds of limiting factors:
Density-dependent limiting factor
Exp. competition, predation,
parasitism, disease
Density-independent limiting factor
Exp. Unusual weather, natural
disasters, seasonal cycles,
certain human activities
biotic
abiotic